So in terms of u value, what can you swap a zinc roof for?

[CalvinHobbes]

The architect gave us a zinc roof but it's too darn expensive. What is the least expensive alternative? Also he said we can use other things as long as they don't effect the u value. The roofer suggested trocal, waiting on a price, has it a better or worse u value?

Edited January 31, 2023 by CalvinHobbes

[PeterW]

Zinc will add naff all - what’s the rest of the build up..? Assume there is OSB and insulation sandwich in there somewhere ..?

[CalvinHobbes]

The plans say 'VMZINC ventilated roof standing seam roof system:
VMZINC PLUS standing seam roofing on 18mm exterior grade
WBP plywood screw fixed to 50 x 50mm treated s/w battens
fixed in line with rafters to provide 50mm deep ventilation path
on VMZINC membrane laid in accordance with the
manufacturers instructions over rafters of prefabricated trusses.
Zinc roofing system to be detailed by VMZINC & agreed with
Architect prior to ordering of material'

Also 

To underside of sloped and flat ceilings provide 15mm plasterboard with skim
finish fixed to 35 x 50mm s/w battens to provide 50mm deep service cavity
over Pro Clima Intello Plus airtight vapour control memebrane with all joints
lapped min 150mm & sealed with Pro Clima Tescon Vana airtight adhesive
tape on 50mm thick Xtratherm / Kingspan PIR rigid insulation board (t/c
0.022W/mk) fixed in accordance with the manufacturers instructions to
underside of the rafters. Airtight barrier to be turned down wall and sealed per
manufacturers recommendations. Completely fill between rafters with Isover
Metac Roll 031 (t/c 0.031W/mk).

Edited January 31, 2023 by CalvinHobbes

[IanR]

Since the ply deck the zinc sits on has a ventilation gap underneath, it's not doing anything for your U value.

 

You can go with an 18mm OSB3 deck and save a little.

 

A good alternative to zinc is Aluminium. Same ductility, so can be hand formed just the same, and more forgiving to condensation issues if there's any ventilation problems.

 

Aluminum was about half the price of zinc for the product, but same labor cost, when I used it. Came in the same price as colourcoat urban steel. 

 

[Kelvin]

Our deck is OSB3 and standing seam metal roof. Got quotes for Colourcoat Urban and Greencoat PLX. 

[Andehh]

Trocal? Looks the same from ground level but massively cheaper, 30% of the price or something.

[IanR]

34 minutes ago, Andehh said:

Trocal? Looks the same from ground level 

 

I've heard that said a few times, but it really doesn't to my eye. There's noticeable differences between a steel standing seam roof and a Zinc or Aluminium roof, but there's a huge difference to a single ply membrane roof with a profile stuck on it.

 

It's a good value option, but doesn't have the same appearance.

[Ralph]

We looked at a membrane roof with a profile and didn't think it looked good at all. In the end we went for Greencoat PLX on the roof and cladding for the first floor and are really happy with it.

 

One thing about steel is that you are likely to get oil canning. Ours is minimal but I've seen some really bad ones and it looks worse with certain colours.

[JohnMo]

I did a Sarnafil standing seam. EPDM the material mechanical fixed to 18mm ply, then seam welded and standing seam mouldings welded.

 

Same effect way less money - 194m2 was £14.7k in early 2021. At the same time I was getting £30k quotes for both zinc and aluminium.

[CalvinHobbes]

17 minutes ago, JohnMo said:

I did a Sarnafil standing seam. EPDM the material mechanical fixed to 18mm ply, then seam welded and standing seam mouldings welded.

 

Same effect way less money - 194m2 was £14.7k in early 2021. At the same time I was getting £30k quotes for both zinc and aluminium.

That looks great, really impressed and you were able to put solar panels on it too. I thought some non metal roofing wouldn't allow that.

Edited February 1, 2023 by CalvinHobbes

[JohnMo]

2 hours ago, CalvinHobbes said:

really impressed and you were able to put solar panels on it too.

Solar panels are in a slate roof. The flatter roofs are sarnafil

[CalvinHobbes]

Ah fair, good job.

[Patrick]

On 31/01/2023 at 23:26, CalvinHobbes said:

The architect gave us a zinc roof but it's too darn expensive. What is the least expensive alternative? Also he said we can use other things as long as they don't effect the u value. The roofer suggested trocal, waiting on a price, has it a better or worse u value?

As others mentioned... U value has nothing to do with the coverage . Whether you put tiles, slate, zinc or metal will make virtually no difference in the u value.

In terms of zinc - most refer to zinc and really mean standing seam. Zinc is the material. Standing seam is the shape of the roof panels. You can have zinc roofs in other shapes (tiles...) And you can have standing seam in other materials

Some previous posted a few alternatives. They are mostly coated metal . Other option would me aluminium.

Then comes the question about installation method...

Traditional standing seam(zinc) is rolled/formed on site from coils. Needs a specialist installer since not everyone owns the forming machine and knows how to work with the material.

Most of the coated steel and aluminium comes in form of pre formed panels .

Then there is only the seam to be closed on site with a seaming machine .

And last not least there are click systems , where you can install without the need of machines/seamers . Panels come preformed .

So it's really

1. Which shape you want (standing seam I presume from your text)

2. Which material do you want ( zinc=most expensive ; Alu= mid price; steel =cheapest)

3.which installation method you prefer (fully trained specialist = most expensive, general builder/roofer= mid price , self install DIY =cheapest) in point 3 : makes not that much sense to buy a DIY system and then hire a trained expert to install it.

You might as well go with zinc in that

Scenario

 

 

[CalvinHobbes]

Thanks, that makes sense.